THE SUN YOU LOOK IS 8 MIN PAST SUN.

you are looking at the sun that is 8 min past sun

you are looking at the screen of your mobile that means the photons emitted from your mobile hits the receptors in the eye that makes you to see this post.in the same way if you are looking at the sun the photons emitted by the sun has to reach your eyes.

But the speed of light is 30,00,00,000 m/s (approx)so it takes 8 min to travel from sun to your eye but actually what sun looks at the time you see sun is different so every time the sun  which you see is the sun that is 8 min before sun.suppose if i remove sun still you can see the sun upto 8 min. And the reason is simple because it takes  8 min to reach light from the sun to the earth.so that means you are looking into the past .

 concept is how far you look into the space that much back you are looking into the time. As the same way sun you look is 8 min older the stars that are present will we so many light years far from us.so the same concept is applied here the stars that you look at night is about years back star.

proxima star which is 4 light years from earth

the proxima star you see is 4 years past 

coming to the stars proxima centaur is the star that is very close to our earth which is 4 light year away from us. so the star that you see is 4 years before star.you don't even know that even that star might be collapsed at that time but you can see the star still alive.so by the help of speed of light have a limit we can look into the past as far as you look that much past you can see.There are even some thousand years ago stars that we can able to see by seeing more far into the space.so this limit in speed of light helps in finding the past of the universe.